1. Field of the Invention
The present invention relates to a metal oxide film having a minutely roughed surface, which is useful as a base or interlayer film of multilayered films on a glass substrate, and a method of forming the same.
2. Description of the Prior Art
Often it is desired to form a metal oxide film having a minutely roughed surface as a base or interlayer film of multilayered films on a glass substrate. This metal oxide film has numerous micro-pits which are scattered on its surface, thereby making the film minutely roughed. With the provision of this metal oxide film, adhesion of the multilayered films to the glass substrate is substantially enhanced, thereby improving abrasion resistance and durability of the multilayered films.
There are conventional methods of minutely roughening or forming numerous micro-pits on a metal oxide film. One example of the methods is etching a metal oxide film surface with hydrofluoric acid, fluorine nitrate or the like. However, this method has the following drawbacks.
Hydrofluoric acid and fluorine nitrate are very hazardous against human body. Therefore, these compounds must be handled very cautiously. This lowers the production efficiency. Furthermore, it is difficult to precisely control the thickness of a metal oxide film and the size of micro-pits.
Another example of the above conventional methods is producing numerous micro-pits on a metal oxide film by the thermal decomposition of an organic polymer added to a metal alkoxide solution. However, this method has the following drawback.
Micro-pits on the metal oxide surface tend to disappear by the densification of the film after baking at a temperature not lower than 400.degree. C.